1. Field of the Invention
The present invention relates to a numerical controller that controls a five-axis machining tool having three linear axes and two rotary axes. In particular, the present invention relates to a numerical controller that performs control so as to move a tool center point position to a position without any error while also compensating the tool orientation (direction) to an orientation (direction) without any error by setting compensation amounts corresponding to errors such as linear axis-dependent translational errors or linear axis-dependent rotational errors dependent on a linear axis position, or rotary axis-dependent translational errors or rotary axis-dependent rotational errors dependent on a rotary axis position, to thereby perform high precision machining.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 2009-151756 discloses a technique of dividing each of a linear axis coordinate system and a rotary axis coordinate system into lattice regions, storing a lattice point compensation vector for each lattice point, and calculating axis-dependent translational compensation amounts and axis-dependent rotational compensation amounts from a linear-axis position and a rotary-axis position based on the lattice point compensation vectors to compensate the linear-axis position.
In the aforementioned technique disclosed in Japanese Patent Application Laid-Open No. 2009-151756, only compensation for the linear-axis position is made. That is, while a tool center point position moves to a position without any error, the orientation (direction) of the tool is still erroneous.
Such compensation of the conventional technique will not cause any problem when machining is performed using a tool center point. However, when machining is performed using a side face of a tool or when machining is performed in the direction of a tool such as drilling, the orientation (direction) of a tool is important and only the compensation to move a tool center point position to a position without any error is not sufficient. Thus, high precision machining cannot be performed according to the conventional technique if there is an error caused by the mechanical system in machining with a side face of a tool or drilling with a five-axis machining tool.
Major errors caused in a five-axis machining tool that machines a workpiece by means of three linear axes and two rotary axes includes the following four errors: (1) a linear axis-dependent translational error dependent on a linear axis position and (2) a rotary axis-dependent translational error dependent on a rotary axis position, which are translational errors; and (3) a linear axis-dependent rotational error dependent on a linear axis position and (4) a rotary axis-dependent rotational error dependent on a rotary axis position, which are rotational errors.